This bug is still present in 2.42.2-5. I have a very short dot file with which it can be reproduced:
digraph { graph [concentrate=true] n1 -> n2 n1 -> n3 n1 -> n5 n1 -> n5 n4 -> n2 n4 -> n3 n2 -> n5 n5 -> n1 } -- Moritz Lenz https://perlgeek.de/ -- https://raku.org/